1. Field of the Invention
The present invention relates to rocket motors. More particularly, the invention relates to the upper stages of a rocket motor system wherein a forward end maneuvering stage is utilized to provide steering and pointing control and ignition, and control of the lower stages.
2. Description of the Prior Art
There is a need for greater control with respect to direction, velocity, and attitude of multi-stage solid propellant rocket motors while at the same time effecting a reduction in system complexity and improving the overall mass fraction. "Mass fraction" is the ratio of the mass of the propellant grain in a rocket motor case to the total mass that could be put in the case if it were completely filled.
The need for such greater control is particularly true of the upper stages of ballistic missiles, the trajectory of which must be corrected to insure accuracy in delivery of the payload, or in multi-stage rocket weapons requiring final intercept maneuvering to counteract evasive movements of the target.
Devices for controlling the direction, velocity and attitude of such upper stages of a rocket motor usually require controlling the flow of gases therethrough by means of valves. In the prior art this has required a special source of gas because high energy or "energetic" propellants that are conventionally used for rocket propulsion produce very high temperatures, and in addition, the gases are corrosive so that they tend to erode, decompose or otherwise render valves inoperative.
Thus, as disclosed in U.S. Pat. No. 3,724,217 granted to Allan J. McDonald on Apr. 3, 1973 and assigned to the assignee of the present invention, there is provided an auxiliary gas generator for supplying gas to control devices for controlling the attitude and direction of a rocket system. Specifically, a solid propellant rocket motor that is extinguishable is coupled by means of pipes and valves with a gas generator that is also extinguishable, and in addition, reignitable. The rocket motor has a forward grain in a top stage and an aft grain in a bottom stage, said grains being in abutting relationship with a central perforation extending the length of the grains. The top stage forward grain is much less energetic than the bottom stage aft grain and produces relatively cool, clean gas that is similar to that produced by the gas generator and which may be valved safely into the attitude and direction control devices. Gas from the gas generator may flow through the rocket motor and gas from the rocket motor may flow to the gas generator depending upon the positions of the valves. Either the gas generator or the rocket motor may contribute, singly or in combination, to propulsion of the rocket system or to operation of the control devices thereof.
Additionally, either the gas generator or the rocket motor can reignite the other. They can both be inoperative at the same time and can b ignited by the igniter of the gas generator.
Since high temperature corrosive gases cause valves to deteriorate, energetic propulsive gases cannot be used as the top stage forward grain in the rocket system of U.S. Pat. No. 3,724,217. Also, he pipe and valve arrangement coupling the gas generator and rocket motor is complex. Additionally, the rocket motor and gas generator remain coupled for the entire flight thus detracting from the mass fraction.
Thus, there exists a need and a demand for improvement in apparatus employed in the prior art for controlling and steering multi-stage rocket motor systems to the end of enabling energetic propellants to be used in the top stage of such systems, if desired or required, while at the same time achieving significant reduction in system complexity and improvement in the overall mass fraction. The present invention was devised to fill the technological gap that has existed in the art in these respects.